University of Cincinnati

UNIVERSITY OF CINCINNATI Date:___________________ I, _________________________________________________________, hereby submit this work as part of the requirements for the degree of: in: It is entitled: This work and its defense approved by: Chair: _______________________________ _______________________________ _______________________________ _______________________________ _______________________________ Bivalve Epibiont Armor: The Evolution of an Antipredatory Strategy A thesis submitted to the Division of Research and Advanced Studies of the University of Cincinnati in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY in the Department of Geological Sciences of the College of Arts and Sciences 2003 by Donna Carlson Jones B.S., State University of New York, College at Fredonia, 1995 M.S., University of Rochester, 1998 Committee Chair: Arnold I. Miller Abstract Conventionally, spines on bivalves and other organisms are thought to serve an antipredatory function; however, this has been tested minimally for epifaunal bivalves, and completed research is contradictory. It is possible that spines do not serve an antipredatory function directly, but provide a substrate for epibionts, those organisms that encrust the outer surface of the bivalve’s shell. Although potentially harmful, coverage by epibionts would benefit the bivalve by concealing it from potential predators. The first portion of this project examined the mechanical behavior of crushed spined and un- spined shells of one epifaunal bivalve (Spondylus regius) in order to ascertain if spines increase the amount of work or force required to fail a shell, elucidating a potential protective function of the spines. A second study demonstrated that epibiont acquisition on various morphologies (including spined, ribbed and smooth varieties) of epifaunal bivalve shells is differential with respect to epibiont species richness and percent coverage. A third study examined the shell morphology of epifaunal bivalves to determine if any correlations exist between this and latitude (and theoretically with predation intensity). To further examine the evolution of interactions between bivalves and their predators with respect to spine development, data were compiled from museum specimens and the paleontological and ecological literature to document changes in bivalve ornamentation through time, water depth and habitat preference. In general, the results here presented indicate that spines and other shell ornamentations likely enhance epibiont coverage and possibly afford some direct physical protection against predators. However, the lack of clear progression in spine characteristics along purported predation gradients may also indicate that hypothesized predation gradients need to be reexamined. ACKNOWLEDGMENTS Many people were instrumental during the completion of the several facets of this project. Those contributing to each are listed below: Chapter 2: I thank Michael LaBarbera for assistance with experimental design and use of laboratory apparatus, Evelyn Mohalski Pence for help drafting Figure 1. Two anonymous reviewers contributed comments during earlier drafts of this chapter. Chapter 3: Eric Powell kindly provided Argopecten, Mytilus and Crassostrea shells. Robert Jones helped with assembly of experimental deployments, data collection and logistics while in the field. The Keys Marine Laboratory provided GPS coordinates and assisted with attaining necessary permits. Tonya Snell served as a dive assistant. David Meyer photographed Figure 1. Kevin Lamprell and an anonymous reviewer made helpful suggestions on earlier versions of this chapter. Chapter 4: Arnold Miller contributed to initial discussions and revisions of early drafts of this manuscript. Evelyn Mohalski Pence drafted Fig. 1 and 2. Elizabeth Harper kindly provided her original categorical species lists. Chapter 5: I would like to thank Evelyn Mohalski Pence for drafting Figure 5.1. Tina Bell and Roger Portell (Florida Museum of Natural History), Paul Greenhall and Warren Blow (Natural History Museum, Smithsonian Institution), Tim White (Peabody Museum, Yale University), Katherine Wetmore Grycewicz (University of California Museum of Paleontology, Berkeley), and Colin Sumrall and Glenn Storrs (Cincinnati Natural History Museum) provided access to specimens. The library staff at the University of Cincinnati, particularly the Interlibrary Loan office, secured much of the literature reviewed. My committee (Richard Aronson, Carlton Brett, Christopher Maples, and David Meyer) and in particular my advisor, Arnold I. Miller, helped with early revisions of all chapters. I specially wish to thank Arnie for allowing me the freedom to delve into questions slightly outside of his current area of research, frequent advice on scientific reasoning and his help with data manipulation. The Paleontological Society, the Geological Society of America, the Ohio Gem and Mineral Show, the Caster Fund (Department of Geology, University of Cincinnati) and the Department of Geology, University of Cincinnati, generously provided funding for this project. A portion of this project was completed while I was a recipient of the Isabel and Mary Neff Fellowship, awarded by the College of Arts and Science, University of Cincinnati. Finally, my husband, Robert Jones, who tolerated my long hours, maintained our home, and provided a pleasant atmosphere deserves high praise. In addition to real assistance in a number of the scientific aspects outlined above, his support as a partner and father was indispensable throughout. Table of Contents ABSTRACT ACKNOWLEDGMENTS TABLE OF CONTENTS……………………………………………………… 1 LIST OF FIGURES…………………………………………………………… 3 LIST OF TABLES……………………………………………………………. 4 LIST OF APPENDICES……………………………………………………… 5 CHAPTER 1: INTRODUCTION…………………………………………….. 6 CHAPTER 2: MECHANICAL PROPERTIES OF SPINES ON THE BIVALVE SPONDYLUS REGIUS LINNAEUS……………………...................... 11 Introduction…………………………………………………………… 11 Material and Methods…………..…………………………………….. 12 Results and Discussion……….……………………………………….. 15 Conclusions…………………………………………………………… 19 CHAPTER 3: EPIFAUNAL BIVALVE SHELL MORPHOLOGY: ITS RELATION TO EPIBIONTS AND PROTECTION FROM PREDATORS………………………………………………………… 20 Introduction…………………………………………………………… 20 Methods……………………………………………………………….. 22 Results………………………………………………………………… 31 Epibiont Characteristics………………………………………… 31 Epibiont Taxon Richness……………………………………….. 32 Epibiont Abundance……………………………………………. 35 Discussion and Conclusions.………………………………………….. 38 CHAPTER 4: LATITUDINAL GRADIENTS OF EPIFAUNAL BIVALVE SHELL MORPHOLOGY AND THEIR RELATION TO PREDATION INTENSITY ………………………………………………………………………… 42 Introduction…………………………………………………………… 42 Methods……………………………………………………………….. 44 Results………………………………………………………………… 48 Discussion…………………………………………………………….. 50 Conclusions…………………………………………………………… 56 CHAPTER 5: VARIATIONS IN SPINE PRESENCE, ABUNDANCE AND MORPHOLOGY ALONG PURPORTED GRADIENTS OF PREDATION INTENSITY ………………………………………………………….. 57 2 Introduction…………………………………………………………… 57 Data Compilations…………………………………………………….. 61 Construction of the Database…………………………………… 61 Variation in Data Sources………………………………………. 63 Data Anaylses………………………………………………………… 66 Latitudinal Variation….………………………………………… 66 Temporal Variation...…………………………………………… 69 Water Depth Variation...………………………………………... 69 Habitat Variation.………………………………………………. 69 Results………………………………………………………………… 70 Latitude…………………………………………………………. 70 Time…………………………………………………………….. 72 Depth……………………………………………………............. 72 Habitat………………………………………………………….. 75 Discussion…………………………………………………………….. 78 Conclusions…………………………………………………………… 84 CHAPTER 6: CONCLUSIONS...…………………………………………….. 85 BIBLIOGRAPHY…………………………………………………………….. 87 APPENDIX A………………………………………………………………… 97 APPENDIX B…………………………………………………………………. 116 3 LIST OF FIGURES Figure 2.1: Diagram of crushing mechanism………………………………….14 Figure 3.1: Treatments used in experiment, prior to deployment……………...23 Figure 3.2: Valve sizes from first collection interval……………………….….25 Figure 3.3: Construction of experiment for testing epibiont preferences……....26 Figure 3.4: Mean epibiont richness of each treatment from each collection interval……………………………………………………………….....33 Figure 3.5: Mean epibiont abundance of each treatment from each collection interval………………………………………………………………....36 Figure 4.1: Examples of epifaunal bivalve morphological types…………..…...46 Figure 4.2: Illustrations of Pinna rugosa…………………………………..…...47 Figure 4.3: Latitudinal diversity gradient for epifaunal bivalves………….…....51 Figure 4.4: Percentage of morphological categories by latitude…………..……52 Figure 4.5: Percentage of spined taxa by latitude……………………………....53 Figure 5.1: Some of the morphologies available for spines on the bivalve, Spondylus……………………………………………………………....59 Figure 5.2: Spine characteristics of Spondylus………………………………....71 Figure 5.3: Differences in spine characteristics by latitude………………….....73 Figure 5.4: Differences in spine characteristics through time…………..………74 Figure 5.5: Differences in spine characteristics by water depth……….……….76 Figure 5.6: Differences in spine characteristics in cryptic and exposed habitats………………………………………………………………....77 4 LIST OF TABLES Table 3.1: Epibiont Taxa identified from each collection interval……………….28 Table 3.2: Statistical comparisons between treatments at each collection interval for mean epibiont richness……………………………………34 Table 3.3: Statistical comparisons between treatments at each collection interval for mean epibiont abundance…………………………………37

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